“Working out shouldn’t be breaking us down,” says Jessica Matthews, assistant professor of exercise science at San Diego Miramar College. “It should be building us up.” Plus, neither sweat nor soreness is a good way to measure how effective your workout is. Instead, here are six science-backed ways to know you're putting in the right kind of effort.

1. Your heart rate says so.

This one's probably the most objective way to measure how good your cardio workout is. “A good workout—by most definitions—involves a heart rate of three-fourths the maximal heart rate, sustained for 20 minutes [or longer],” says Daniel Vigil, M.D., who specializes in sports medicine at the Ronald Reagan UCLA Medical Center.

So how do you calculate that? Experts once used a simple formula: 220 minus your age equals your max heart rate. However this formula tends to overestimate your max heart rate, and these days, trainers often rely on another equation:

For example, if you're 23 years old, your max heart rate would be about 191 bpm (beats per minute), according to the formula above. Now, calculate three-quarters of that to find your target: about 143 bpm. To keep track of your stats and your progress, consider using a heart rate monitor (it’s totally worth it, trust us).

One more note about heart rate: If you wake up the next morning and your resting heart rate is still slightly above normal, you're not fully recovered from your last workout. Your resting heart rate can be a great indicator of overtraining (more on that below).

Heart rate is a great measurement for cardiovascular fitness, but the same doesn't necessarily apply to strength training. If you're lifting heavy weights, taking adequate breaks between sets is vital to building strength.

2. You feel stronger immediately.

Here’s where a little thing called rate of perceived exertion (RPE for short) comes in. Unlike measuring heart rate, RPE is subjective—it’s basically how hard you think you’re working. And there are two different RPE scales you can follow: Some pros use a zero to 10 scale, while others use the Borg Scale—one that goes from six to 20. On either scale, the higher the number you rate your workout, the harder you feel you’re working.

If you're being honest with yourself and think you’ve been working at an eight or a nine, or at about a 17 on the Borg scale, you’re likely crushing it. That hard work and toughness of the workout is translating to you feeling stronger and better—not beaten down. “You’re at a point where you could max out, but you’re not quite there yet,” says Rebecca Kennedy, a NYC-based fitness expert and founder of A.C.C.E.S.S. Because remember: Maxing out and collapsing on the floor isn’t the goal of a good workout.

In fact, it's a great idea to throw in an easy workout (or maybe a full day of rest!) after a tough workout. Recovery days—which can be mentally tough for those who love the gym—are just as important as the days you lift more weight, run faster, or jump higher.

3. You recover from intense intervals quickly.

Most people probably pay attention to the intense portions of interval training—and with good reason: Lots of studies show that working hard for varying intervals can burn a ton of calories. But how quickly your heart recovers during the low-intensity periods of your workout is pretty telling in terms of how effective your training is. “A heart that is healthy will recover at a quicker rate than one that is not healthy or not accustomed to regular exercise,” Kennedy says. If you notice your heart rate dropping down in one minute or less during your rest periods, you’re on the right track.

4. You felt challenged in new ways.

This one's tricky: While you want to feel like you're working hard during your workout, you never want to get to “the end of the rope,” Kennedy says. Your goal is to work at a level that feels challenging—it should be a struggle to crank out your last reps, Matthews says.

Another good barometer: the talk test. If it's difficult to get out a sentence or carry on a convo with your workout pal, you're working at a challenging level. If you're gasping for air and can't utter a word, it's time to pull back the intensity.

5. You get better zzzs.

One of the coolest benefits of a good workout? It generally makes you feel less sleepy. But that's not all: Research suggests that sleep quality improves after even a single workout session, so you may score better shut-eye after hitting the gym. If you’re noticing the exact opposite effect (e.g. you kill it at CrossFit on the regular and still find yourself tossing and turning), that might be a sign you’re overtraining, Matthews says. “Exercise should help you get more restful sleep at night, but if you’re going to an extreme, you might be sleeping less,” she says.

6. You're more focused the rest of the day.

This may come as no surprise, but experts agree sweat sessions should give you a mental boost, not just a physical one—and that’s another sign of a great workout. “You want to feel better walking out than walking in," Kennedy says. That means happier (yay, endorphins!) and more confident. Your productivity, focus, and clarity should also improve afterward, Matthews says. The best part? Unlike waiting to see the scale tip in your favor or your clothes fit better, it doesn’t take long to reap the mental benefits of a good workout. In fact, psychology experts say you’ll experience a mood boost as soon as five minutes post exercise. Talk about instant gratification.